The present invention relates generally to a thermoplastic polymer blend composition which contains an amount of a thermoplastic chlorinated polyethylene resin. The present invention also relates to a membrane formed from the polymer blend composition. The membrane is suitable for use in single-ply roofing applications.
Single-ply roofing membranes are suitably applied to a roofing structure as a plurality of strips rather than as a single large continuous membrane. A single large membrane would be difficult to manufacture and even more difficult to install.
Each strip is adhesively bonded to adjacent strips during installation to form a continuous membrane. In practice, there is a small overlap of one strip over an adjacent strip to facilitate bonding. The overlap is more commonly referred to as a seam. Adhesive bond strength of the seams is readily measured.
A single-ply roofing membrane, when installed on a roofing structure, is beneficially anchored to the roofing structure at several points thereof. In particular, the membrane is anchored to the edges of the roofing structure.
It has been found that single-ply roofing membranes experience a phenomenon known as "temperature induced load" during use, particularly in northern states. "Temperature induced load" is a measure of a force which a membrane exerts due to contraction upon being cooled from ambient temperatures of about 70.degree. Fahrenheit (21.degree. Centigrade) to subfreezing temperatures of about -30.degree. Fahrenheit (-34.degree. Centigrade).
Those skilled in the art will appreciate that "temperature induced load" is primarily dependent upon polymer composition of the membrane. They will also understand that "temperature induced load" may equal or exceed the adhesive bond strength of membrane seams.
When the temperature induced load exceeds bond strength of the seams of an anchored membrane, it follows that rupture of the seams may occur. Once the seams are ruptured, the membrane has a markedly reduced effectiveness.
In order to ensure membrane continuity, several possible solutions exist. One possible solution involves use of a stronger adhesive to increase bond strength of the seams. A second possible solution involves modification of membrane polymer composition to reduce temperature induced load. A third possible solution is a combination of the aforementioned solutions.